Which geographic feature separates Washington's eastern and western wine regions?

• A. Olympic Mountains
• B. Rocky Mountains
• C. Cascade Mountains
• D. Coastal Range

Answer: (C)

The main idea is how a mountain range can create a climate divide that shapes where and how grapes grow. The Cascade Mountains run north-south through Washington and act as the key barrier between the wetter, cooler western side and the drier, sunnier eastern side. That rain-shadow effect produces distinctly different vineyard climates on either side, which is exactly why the Cascades separate Washington’s eastern and western wine regions.

The other features don’t serve as this regional divider. The Olympic Mountains are on the western edge but don’t form the broad east–west boundary for the state’s wine regions. The Rocky Mountains are further east and aren’t the dividing feature within Washington. The term Coastal Range isn’t the standard defining barrier in Washington viticulture.